Synthesis and Antifeedant Activity of Racemic and Optically Active Hydroxy Lactones with the p-Menthane System

Antifeedant Potential of Geranylacetone and Nerylacetone and Their Epoxy-Derivatives against Myzus persicae (Sulz.)

Geranylacetone and nerylacetone are natural sesquiterpenoids, which play various roles in plant-insect interactions, including the deterrent and repellent effects on herbivores. The structural modifications of natural compounds often change their biological activities. The aim of the study was to evaluate the effect of geranylacetone, nerylacetone and their epoxy-derivatives on the probing and settling behavior of Myzus persicae (Sulz.) (Hemiptera: Aphididae). The no-choice test using the Electrical Penetration Graph (EPG) technique showed that the probes before the first phloem phase were usually shorter than 3 min, which means that they were terminated within the epidermis and/or outer layers of mesophyll. This resulted in a tendency to delay the initiation of the phloem phase in aphids, which reflects a weak preingestive deterrent activity of the studied compounds at the level of non-vascular tissues. Most M. persicae showed bouts of sustained phloem sap ingestion. However, the 24-h free-choice test demonstrated that aphids did not settle on the leaves treated with geranylacetone, nerylacetone, and their epoxy-derivatives. The refusal to settle after the consumption of phloem sap on treated plants indicated that the studied compounds had postingestive deterrent activity. The epoxidation of geranylacetone and nerylacetone did not evoke significant changes in their activity profiles.

Antimicrobial Activity of Lactones

The development of bacterial resistance to antibiotics and the consequent lack of effective therapy is one of the biggest problems in modern medicine. A consequence of these processes is an urgent need to continuously design and develop novel antimicrobial agents. Among the compounds showing antimicrobial potential, lactones are a group to explore. For centuries, their antimicrobial activities have been used in folk medicine. Currently, novel lactone compounds are continuously described in the literature. Some of those structures exhibit high antimicrobial potential and some are an inspiration for design and synthesis of future drugs. This paper describes recent developments on antimicrobial lactones with smaller ring sizes, up to seven membered ε-lactones. Their isolation from natural sources, chemical synthesis, synergistic activity with antibiotics, and effects on quorum sensing are presented herein.

Synthesis of novel phytol-derived γ-butyrolactones and evaluation of their biological activity

The synthesis of phytol-derived γ-butyrolactones as well as their evaluation for deterrent activity towards peach-potato aphid Myzus persicae and antiproliferative activity against four selected cancer cell lines are reported. Products were obtained in good yields (19-96%) and their structures were fully characterized by spectroscopic data (NMR, HRMS). Four synthesized δ-halo-γ-lactones (4-7) are new and have not been previously described in the literature. In the choice test phytol (1) appeared deterrent to M. persicae, whereas modifications of its structure did not cause the avoidance of the treated leaves by the aphids. In contrast, aphids were attracted to the leaves treated with the new trans-δ-chloro-γ-lactone (6). Electrical Penetration Graph (EPG) technique applied to explore the aphid probing and feeding activity revealed that neither phytol nor lactone 6 affected aphid probing and the consumption of phloem sap, which means that both phytol and the lactone 6 might have acted as postingestive modifiers of aphid behavior. The results of in vitro antitumor assays showed that obtained phytol derivatives exhibit cytotoxic activity against studied cancer cell lines (leukemia, lung and colon carcinoma and its doxorubicin resistant subline). Halolactones 4-6 were identified as the compounds, which arrest cell cycle of leukemia cells mainly in G2/M and S phases.

Antiproliferative, Antimicrobial and Antiviral Activity of β-Aryl-δ-iodo-γ-lactones, Their Effect on Cellular Oxidative Stress Markers and Biological Membranes

The aim of this work was the examination of biological activity of three selected racemic cis-β-aryl-δ-iodo-γ-lactones. Tested iodolactones differed in the structure of the aromatic fragment of molecule, bearing isopropyl (1), methyl (2), or no substituent (3) on the para position of the benzene ring. A broad spectrum of biological activity as antimicrobial, antiviral, antitumor, cytotoxic, antioxidant, and hemolytic activity was examined. All iodolactones showed bactericidal activity against Proteus mirabilis, and lactones 1,2 were active against Bacillus cereus. The highest cytotoxic activity towards HeLa and MCF7 cancer cell lines and NHDF normal cell line was found for lactone 1. All assessed lactones significantly disrupted antioxidative/oxidative balance of the NHDF, and the most harmful effect was determined by lactone 1. Contrary to lactone 1, lactones 2 and 3 did not induce the hemolysis of erythrocytes after 48 h of incubation. The differences in activity of iodolactones 1–3 in biological tests may be explained by their different impact on physicochemical properties of membrane as the packing order in the hydrophilic area and fluidity of hydrocarbon chains. This was dependent on the presence and type of alkyl substituent. The highest effect on the membrane organization was observed for lactone 1 due to the presence of bulky isopropyl group on the benzene ring.

Chemoenzymatic Synthesis of Enantiomeric, Bicyclic δ-Halo-γ-lactones with a Cyclohexane Ring, Their Biological Activity and Interaction with Biological Membranes

Starting from 1-acetyl-1-cyclohexene, three enantiomeric pairs (ee ≥99%) of bicyclic δ-halo-γ-lactones with cyclohexane ring were obtained in five-step synthesis. The key stereochemical steps were lipase-catalyzed kinetic resolution of racemic 1-(cyclohex-1-en-1-yl) ethanol followed by transfer of chirality to ethyl 2-(2-ethylidenecyclohexyl) acetate in the Johnson-Claisen rearrangement. Synthesized halolactones exhibited antiproliferative activity towards canine B-cell leukemia cells (GL-1) and canine B-cell chronic leukemia cells (CLB70) and the most potent (IC₅₀ 18.43 ± 1.46 μg/mL against GL-1, IC₅₀ 11.40 ± 0.40 μg/mL against CLB70) comparable with the control etoposide, was (1R,6R,1'S)-1-(1'-chloroethyl)-9- oxabicyclo[4.3.0]nonan-8-one (8b). All halolactones did not have a toxic effect on erythrocytes and did not change the fluidity of membranes in the hydrophobic region of the lipid bilayer. Only weak changes in the hydrophilic area were observed, like the degree of lipid packing and associated hydration. The racemic halolactones were also tested for their antimicrobial properties and found to exhibit selectivity towards bacteria, in particular, towards Proteus mirabilis ATCC 35659.

Novel Hydroxy- and Epoxy-cis-Jasmone and Dihydrojasmone Derivatives Affect the Foraging Activity of the Peach Potato Aphid Myzus persicae (Sulzer) (Homoptera: Aphididae)

Jasmonates show great potential in sustainable agriculture due to their various roles in natural mechanisms of plant defense, and because they are non-toxic, non-mutagenic, and easily metabolized. The aim of the study was to explore structure⁻activity relationships of dihydrojasmone, cis-jasmone, and their derivatives at the plant⁻aphid interface. We focused on the behavioral responses of aphids, following the exogenous application of natural jasmonates and their derivatives to the host plants. Aphid probing behavior was examined using an electrical penetration graph technique (EPG). The chemoenzymatic transformation of cis-jasmone and the activity of two new derivatives are described. The application of cis-jasmone, dihydrojasmone, the hydroxyderivatives, epoxyderivatives, and alkyl-substituted δ-lactones hindered the foraging activity of Myzus persicae (Sulz.) (Hemiptera: Aphididae) during early stages of probing at the level of non-phloem tissues. The application of saturated bicyclic epoxy-δ-lactone enhanced plant acceptance by M. persicae. Jasmonate derivatives containing a hydroxy group, especially in correlation with a lactone ring, were more active than natural compounds and other derivatives studied. Jasmonates of the present study are worth considering as elements of sustainable aphid control as components of the "push⁻pull" strategy.

Biotransformation of Bicyclic Halolactones with a Methyl Group in the Cyclohexane Ring into Hydroxylactones and Their Biological Activity

The aim of this study was the chemical synthesis of a series of halo- and unsaturated lactones, as well as their microbial transformation products. Finally some of their biological activities were assessed. Three bicyclic halolactones with a methyl group in the cyclohexane ring were obtained from the corresponding γ,δ-unsaturated ester during a two-step synthesis. These lactones were subjected to screening biotransformation using twenty two fungal strains. These strains were tested on their ability to transform halolactones into new hydroxylactones. Among the six strains able to catalyze hydrolytic dehalogenation, only two (Fusarium equiseti, AM22 and Yarrowia lipolytica, AM71) gave a product in a high yield. Moreover, one strain (Penicillium wermiculatum, AM30) introduced the hydroxy group on the cyclohexane ring without removing the halogen atom. The biological activity of five of the obtained lactones was tested. Some of these compounds exhibited growth inhibition against bacteria, yeasts and fungi and deterrent activity against peach-potato aphid.

Stereoselective yeast-mediated reduction of trans-5-(1'-oxo-3'-methylbutyl)-3-methyldihydrofuran-2-one: production of chiral intermediates for the synthesis of β-secretase inhibitors

OBJECTIVE

To investigate the usefulness of yeast strains to the production of chiral hydroxylactones, important synthons in the synthesis of β-secretase inhibitors.

RESULTS

Strains Rhodotorula glutinis KCh 242, Rhodotorula rubra KCh 82, Rhodotorula marina KCh 77 and Saccharomyces cerevisiae KCh 464 reduced racemic trans-5-(1'-oxo-3'-methylbutyl)-3-methyldihydrofuran-2-one (4) according to the Prelog's rule to afford preferentially the stereoisomers with S configurations at C-1'. R. marina KCh 77 and R. glutinis KCh 242 exhibited selectivity towards 3S, 5R enantiomer of the substrate, whereas R. rubra KCh 82 and S. cerevisiae KCh 464 preferred the reduction of its antipode. The highest yield of 3R,5S,1'S-hydroxylactone 3c (78 %) was obtained with R. rubra KCh 82.

CONCLUSIONS

Different stereoisomers of trans-5-(1'-hydroxy-3'-methylbutyl)-3-methyldihydrofuran-2-one and its 5-substituted analogues are produced as important intermediates in the synthesis of drugs for the therapy of Alzheimer's disease.